1. Field of the Invention
This invention relates to a king pin assembly, and more particularly relates to a longitudinally adjustable king pin assembly of a fifth wheel trailer for attachment to the fifth wheel assembly on a tractor-trailer.
2. Description of the Related Art
Most large commercial transports include a tractor and a trailer attached to the tractor. The tractor consists of an engine, cab for the driver, transmission and drive wheels, and a “fifth wheel” which is a horizontal, flat circle with a pie-shaped wedge cut out of its rear-most portion. A downward pointing king pin at the front of a trailer slips into the pie-shaped opening in the fifth wheel and is clamped into position by the fifth wheel. The fifth wheel then bears the pulling load of the tractor and, as the trailer pin is cylindrical in shape, it allows the tractor to hinge at the pin-fifth wheel connection for turns.
Conventionally, the fifth wheel structure on a truck or tractor may be longitudinally adjustable on the tractor unit by means of, for example, an air pressured power pin mounted on the fifth wheel that fits into various slots on the deck of the tractor, allowing the fifth wheel to be moved forwards and backwards.
Several advantages arise if the king pin can be provided with a measure of longitudinal adjustment. For example, this would allow the driver of the vehicle to change the weights on the driving axles of the tractor and the forward-most set of wheels on the trailer, such that the driver might increase traction on the drive wheels when necessary.
As well, relative adjustment of the location of the king pin in the longitudinal direction permits the driver to also adjust the load on the trailer so that all of the axles on the tractor and trailer are of legal weight, rather than one being over legal weight and requiring either special permits or the payment of fines if no permit is available or if the weight is in excess of the permit.
Assignee's earlier U.S. Pat. No. 4,923,204 represented vast improvements in the adjustable king pin assembly art. In assignee's earlier U.S. Pat. No. 4,923,204, the slider bar and king pin thereof sometimes required repair or replacement, as in most king pin assemblies. The slider bar and king pin attached thereto were difficult to repair or replace in Assignee's earlier structure in that the structure required significant cutting and disassembly. The instant invention enables the slider bar and king pin structure to be easily removed from the assembly for repair and/or replacement thereof.